In a recording and reproducing apparatus such as an optical disk drive for recording large-volume data, a pulse row that changes in accordance with data is converted into a pulse row finer than a minimum data unit. The fine pulse row is used to modulate the intensity of a laser beam. When intensity-modulated laser beam is focused onto a recording medium, heat is applied to the recording medium. This changes physical characteristics of the recording medium, thereby forming recorded marks. In this way, data is recorded in the recording medium. Setting data on a pulse width required for recording (required to form the recorded marks) and setting data on a recording condition for performing recording compensation with respect to, for example, the power of each laser beam are recorded in advance as predetermined data in an optical disk (in the following description, an optical disk may be simply referred to as “disk”).
Incidentally, increasingly densified optical disks require more accurate setting, such as a setting in which a standard recording condition is set with respect to each mark length (size of a recorded mark in the track direction) or with respect to each combination of mark length and space (between recorded marks) length. In high-density recording, the mark length and space length are short. Therefore, when heat of the laser beam is applied so as to form a mark, the heat affects not only the mark but also adjacent marks through spaces. As a result, the mark and the adjacent marks are distorted. This is the reason why accurate setting is required.
However, if recording and reproducing apparatuses (in the following description, a recording and reproducing apparatus may be simply referred to as “apparatus”) are mass produced, the apparatuses do not always have the same characteristics, because the members used may have different characteristics, and because the production environment can be different, for example. For example, laser drive means and a head provided with a laser, which are members associated with recording, can be different from apparatus to apparatus. This is primarily due to difference in laser characteristics. If there is difference in laser characteristics, the pulse width can be different even if the waveform of the current supplied to the laser of each apparatus is the same. As a result, the waveform of the emitted light is not always the same. The difference in laser characteristics include difference in laser drive means (laser drive circuit), in addition to difference in the laser itself. Likewise, optical disks are also different in characteristics when mass produced. Therefore, the shape of the recorded marks is not always the same even if recording is performed under the same condition with respect to each optical disk.
Thus, if mass-produced optical disks and recording and reproducing apparatuses having different characteristics are used in certain combination, recording and reproduction cannot be performed appropriately, even if standard disks having standard characteristics are used under a standard recording condition determined by a standard apparatus having standard characteristics. This results in deterioration of quality.
If such disks that are manufactured under sufficient quality control and therefore have little difference in characteristics are used, no significant problem will arise. However, if the recording pulse standard condition recorded in the disks in advance has a large gap with disk performance, the disks cannot demonstrate their characteristics even if the recording pulse standard condition is read out of the disks and reproduced with high fidelity.
To solve these problems, Japanese Publication for Laid-Open Patent Application, Tokukai 2000-200418 (publication date: Jul. 18, 2000) (hereinafter “Patent Publication 1”) discloses a method of determining a recording condition by modifying the standard recording condition. In this method, in an optical disk in which a standard recording pulse conditions are recorded in advance in a specific zone, positional data with respect to all combinations or one combination of the mark length and space length, (all the combinations or one combination of the mark length and space length are part of the standard recording pulse condition) is changed in advance by a predetermined amount. By so doing, a corrected value of the standard recording pulse condition that makes jitter of recording and reproducing signals not higher than an acceptable value is set as the recording pulse condition of the recording and reproducing apparatus.
According to this method, to solve the problem that the pulse width changes primarily due to the difference in laser characteristics, all the combinations of mark length and space length are changed uniformly by the predetermined amount. To solve the problem that, if the recording pulse standard condition recorded in the disks in advance has a large gap with disk performance, the disks cannot demonstrate their characteristics even if the recording pulse standard condition is read out of the disks and reproduced with high fidelity, part of all combinations of mark length and space length are changed individually.
According to a method disclosed in Japanese Publication for Laid-Open Patent Application, Tokukai 2000-182244 (publication date: Jun. 30, 2000) (hereinafter “Patent Publication 2”), testwrite is performed in accordance with a plurality of recording powers and a plurality of laser emitted light waveform rules (pulse widths), and both a recording power and a pulse width are determined in accordance with a result of the testwrite.
Publication 1 teaches that, in one method for setting a recording pulse condition, all the combinations of the mark length and space length (all the combinations of the mark length and space length are part of the standard recording pulse condition) are changed uniformly or individually by a predetermined amount.
However, for example, Publication 1 does not consider such cases where the difference in laser characteristics, which requires to change the recording pulse condition uniformly, and the difference in disk characteristics, which requires to change the recording pulse condition individually, are both present. Therefore, in such cases where the difference in laser characteristics and the difference in disk characteristics are both present as described above, one problem is that the recording condition cannot be set efficiently, and long time is required to set the recording condition.
Moreover, according to Patent Publication 1, only a condition on pulse width is optimized, and a condition on laser power is not optimized, in setting the recording pulse condition. Like the pulse width, the laser power influences the quality of reproduction signals. Therefore, by also optimizing the condition on laser power, the quality of reproduction signals can be improved more efficiently. In this respect, Publication 1 has a room for further improvement.
According to the method of Patent Publication 2, testwrite is performed by using all combinations of recording power and pulse width, without even handling the difference in laser characteristics and the difference in disk characteristics separately. Therefore, enormous process time is required in order to determine the recording power and pulse width, and recording zone for the testwrite is required. According to another method disclosed in Patent Publication 2, optimal recording power is determined through testwrite, and then testwrite is performed by using a plurality of pulse widths. In accordance with the result of the testwrite, both the recording power and the pulse width are determined. However, since the test write is performed by using conditions of all pulse widths, this method also has the problem that enormous process time is required in order to determine the recording power and pulse width, and recording zone for the testwrite is required. Moreover, since conditions on mark length or on a combination of mark length and space length are not considered, this method has a problem that, even if there are differences in characteristics on the apparatus side and on the disk side, the differences cannot be dealt with.